This invention relates to direct current switching apparatus and more particularly to direct current electromagnetic contactors. Still more particularly, the invention relates to contactors of the aforementioned type which are especially suitable for application in D.C. traction equipment for interrupting high voltages and high currents.
In D.C. switching apparatus, an electric are is generated between separating contacts. The voltage of such arc is caused to increase, thereby driving the current in the arc down in order to extinguish the arc and achieve circuit interruption. There are numerous techniques known in D.C. switching technology to extinguish arcs, such techniques often being used in various combinations. For example, lengthening the are generates a rise in are voltage. Separating the arc into a plurality of smaller segments increases its voltage and tends to cool the are. Confining the arc and compressing it to flatten the cross sectional shape thereof also increases the arc voltage. Still another technology is to subject the arc to materials which emit a quenching gas when subjected to the heat of the arc. U.S. Pat. No. 3,511,950 issued May 12, 1970 to D. R. Boyd discloses a direct current electromagnetic contactor having an are chute which utilizes the aforementioned arc interruption technologies to divide the arc into two initial segments and to move the arc segments into respective left and right-hand arc extinguishing chambers. This invention relates to improvements thereover.